Inclusion Criteria:

• Have a pathologic diagnosis of advanced solid tumors
• After MTD is established, patients must have a measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) criteria
• Be greater than or equal to 18 years old
• Not eligible for therapy of higher curative potential
• Have a Karnofsky Performance Status (KPS) greater than or equal to 70
• Have an estimated life expectancy of greater than or equal to 12 weeks
• Have a negative serum or urine pregnancy test within 7 days of study enrollment (if patient is a female of childbearing potential)
• Male and female patients who are fertile must agree to use an effective barrier method of birth control (latex condom, diaphragm, cervical cap, etc.) to avoid pregnancy
• Sign a written informed consent form
• Able to comply with study procedures and follow-up examinations
• Have adequate organ function as indicated by the following laboratory values, obtained within 2 weeks prior to registration: ANC: greater than or equal to 1.5 × 10 9th/L; Platelets: greater than or equal to 100 × 10 9th/L; Serum bilirubin: less than 2.0 mg/dL; AST and ALT: less than 3 x ULN (Institutional Upper Limit of Normal) without liver involvement OR less than 5 x ULN(*) with liver involvement; Serum creatinine: less than 2.0 mg/dL; Echocardiogram shortening fraction: greater than or equal to 28%(Not on pharmacologic support); or Ejection fraction greater than or equal to 50% (Not on pharmacologic support).

Exclusion Criteria:

• Received previous treatment with clofarabine.
• Have an active, uncontrolled systemic infection considered opportunistic, life threatening, or clinically significant at the time of treatment.
• Prior malignancy with less than a 2-year disease-free interval, except for adequately treated basal cell or squamous cell skin cancer; or in situ cancer of the cervix.
• Are pregnant or lactating.
• Have a psychiatric disorder(s) that would interfere with consent, study participation, or follow-up.
• Have received any chemotherapy, major surgery, or irradiation, whether conventional or investigational, < 4 weeks before enrollment in this study (6 weeks for mitomycin-C or nitrosourea) and/or have not recovered from acute toxicities of all previous therapy prior to enrollment.
• Have any other severe concurrent disease, which, in the judgment of the investigator, would make the patient inappropriate for entry into this study (eg, uncontrolled severe insulin-dependent diabetes, uncontrolled hypertension, transient ischemic attacks, uncontrolled symptomatic coronary artery disease, etc.).
• Have received prior radiation therapy to greater than or equal to 25% of the bone marrow (eg, no whole pelvic irradiation is allowed) and have not recovered from the acute side effects of radiotherapy.
• Have received prior radiation therapy to the mediastinal region.
• Have a broncho-alveolar pattern evident on chest x-ray.
• Have symptomatic or untreated central nervous system (CNS) metastases.